Have you got a photo with the bottom pulley removed?
Would it be possible to modify a 2wd bottom pulley of a Cosworth?
If not i'm sure you could have an alloy one custom made.

Also an another idea does the power steering pump pulley line up with either of the two V's on the excisting bottom pulley might just be a case of putting a longer belt round the Bottom Pulley, Water Pump and then the PAS pulley.

Rich